Characteristics of Luffa sponge-immobilized pectinase from Aspergillus niger FTR 002 and its use in the continuous clarification of orange juice in packed-bed column bioreactor

Background and Objective One of the major challenges of linking enzymes to insoluble support matrices is the use of non-naturally occurring support matrices that are expensive and not readily accessible, which most times are not easy to handle with the process needing several steps. Therefore, naturally-occurring materials that are cheap, available and need a little or no modifications with the potentials to act as support matrices for enzyme immobilization were investigated. Material and Methods: In this study, coconut fibers, pseudo stems of banana and plaster of Paris luffa sponges as appropriate carriers for the immobilization of pectinase produced by Aspegillus niger FTR 002 were investigated and purified using chromatographic techniques, physical adsorption and covalent bonding with glutaraldehyde. Characteristics of native and immobilized enzyme preparations were studied and then used in the clarification of juice using packed-bed column reactor and standard procedures. Results and Conclusion: Of the four materials in this study, sponge included the highest immobilization rate. Free and sponge-immobilized pectinase preparations were characterized and results recorded a temperature optimum of 50 degrees C for the two enzyme preparations. A shift in pH optima from 6.0 to 5.0 by the pectinase was observed after immobilization on sponge. The Km and Vmax of the free and immobilized pectinases included 2.33 mM and 0.018 mu M/min and 1.612 mM and 0.019 mu M/min respectively. Reusability studies showed that the immobilized enzyme included approximately 55% of its initial activity after 15 repeated cycles in batch operation. Orange juice clarification using sponge-immobilized pectinase using packed-bed column reactor at a flow rate of 0.5 ml/min showed that the immobilized catalyst included 40% of its clarification capacity after 80 h of continuous operation. These findings indicate that the pectinase immobilized on sponge includes promising potentials as a clarifying catalyst in fruit-juice industries.